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<h1>Getting Started</h1>
<p>OPC is best understood by example. The following guide provides you 
 with some very basic overview concepts, along with some simple exercises 
 to learn OPC technology by demonstration.</p>
<h2>Launching the OPC UA Server &amp; Client</h2>
<ol type="1">
	<li><p>Several OPC UA Servers and Clients have been installed as part 
	 of this package. First, we will launch the <a href="DAServerOverview.htm">DA 
	 Server</a> and then the <a href="DAClientOverview.htm">DA Client</a></p></li>
	<ol type="1">
		<li><p>Both applications can be found here:<br />
		START &gt; All Programs &gt; OPC Foundation &gt; Unified Architecture 
		 &gt; Sample Applications &gt; Technology Samples.</p></li>
		<li><p>First, launch the server: <span style="font-weight: bold;">DA 
		 Server</span>.</p></li>
		<li><p>Second, launch the client: <span style="font-weight: bold;">DA 
		 Client</span>.</p></li>
	</ol>
	<li><p>Both applications should now be open on-screen.</p></li>
</ol>
<h2>Connecting a Client to a Server</h2>
<ol type="1">
	<li><p>The DA Server will show its <span style="font-style: italic;">endpoint</span> 
	 at the top of the window. See <a href="DAServerOverview.htm#gui">DA 
	 Server GUI</a>. Using the mouse, simply highlight the endpoint and 
	 then copy it to the Windows clipboard.</p></li>
	<li><p>Switch to the <?rh-udv_start name="genClt" ?>Generic UA Client<?rh-udv_end ?> 
	 and then paste the endpoint into the <span style="font-style: italic;">endpoint 
	 </span>field. See <a href="DAClientOverview.htm#gui">DA Client GUI</a>.<br />
	<?rh-cbt_start condition="Member" ?>TIP: The following step-by-step 
	 tutorial shows <?rh-cbt_end ?><?rh-cbt_start condition="Member" ?><a 
	 href="HTTPS_Connectivity.htm">HTTPS connectivity</a><?rh-cbt_end ?><?rh-cbt_start condition="Member" ?>.<?rh-cbt_end ?></p></li>
	<li><p>Click the <span style="font-weight: bold;">Connect</span> button, 
	 which is displayed at the far-right of the endpoint address field.</p></li>
	<li><p>The Server will validate the client's request and the connection 
	 should be established.</p></li>
	<?rh-cbt_start condition="Member" ?><li><p>If the connection is <span 
	 style="font-style: italic;">rejected</span> by the server, then this 
	 will almost certainly be a certificate trust issue. See <?rh-cbt_start condition="Member" ?><a 
	 href="Troubleshooting.htm">Troubleshooting</a><?rh-cbt_end ?> section 
	 for tips on fixing this problem.</p></li><?rh-cbt_end ?>
</ol>
<h2>Browsing the Server's Address Space</h2>
<p>A powerful feature of OPC is the ability for a Client to browse the 
 Server and see the data that is currently available. All data is stored 
 in a structure similar to a file and folder concept, except in OPC these 
 are called &quot;Nodes&quot;.</p>
<ol type="1">
	<li><p>In this exercise we will use the DA Client only.</p></li>
	<li><p>The main visible area of the client window shows the navigation 
	 area.</p></li>
	<li><p>Simply expand/collapse the visible nodes to continue the navigation 
	 experience. See <a href="Address_Space_Navigation.htm">Address Space 
	 Navigation</a> for more details.</p></li>
</ol>
<h2>Reading Data</h2>
<p>You can acquire data on-demand by using a <span style="font-style: italic;">Read</span>, 
 which<span style="font-style: italic;"> </span>allows you<span style="font-style: italic;"> 
 </span>to read 1..n Nodes in a single call. This is very useful for obtaining 
 a &quot;snapshot&quot; of the current values. Many OPC Servers will actually 
 obtain the data from the underlying device/system prior to returning the 
 values to the client.</p>
<ol type="1">
	<li><p>In this exercise we will use the DA Client only.</p></li>
	<li><p>Simply locate a Node within the main navigation area and then 
	 click on it, this will automatically invoke a Read.</p></li>
	<li><p>The attributes and values associated with the selected node 
	 will be displayed on the right-side of the window.</p></li>
</ol>
<h3>Exercises</h3>
<ul type="disc">
	<li><p>Read 1 node.</p></li>
	<li><p>Read a node in a different location.</p></li>
</ul>
<h2>Writing Data</h2>
<p>In addition to acquiring data, Clients can provide data to a Server 
 too via a Write operation. You can write to 1..n Nodes within a single 
 call, and can specify the value and/or quality for each node.</p>
<ol type="1">
	<li><p>In this exercise we will use the DA Client only.</p></li>
	<li><p>Simply locate a Node within the main navigation area and then 
	 right-click (to activate the context menu) and choose Write.</p></li>
	<li><p>Specify a value to write and then click OK.</p></li>
	<li><p>The value will be immediately written to the node; some nodes 
	 are read-only whereas others are read/write so be prepared to see 
	 dialogs indicating a write failure.</p></li>
</ol>
<h3>Exercises</h3>
<ul type="disc">
	<li><p>Write to 1 node of each data-type.</p></li>
	<li><p>Write to 3 nodes (while varying the data type) in a single call.</p></li>
</ul>
<h2>Subscribing to Data</h2>
<p>Subscriptions are the most powerful and optimized method of continuous 
 data acquisition. You cannot compare a subscription to continuous Read 
 operations. Subscriptions cause a Server to poll a device on-behalf of 
 the Client, and when the Server detects that a Node's value has changed 
 then the Server will send the new information to the Client. This method 
 reduces the load on the Client, reduces the load on the Server, and can 
 also reduce the load on the underlying device, particularly when multiple 
 Clients are subscribing to the same nodes (and at the same frequency).</p>
<ol type="1">
	<li><p>In this exercise we will use the DA Client only.</p></li>
	<li><p>Simply locate a Node within the main navigation area and then 
	 right-click (to activate the context menu) and choose Monitor.</p></li>
	<li><p>The node will show updated values as they occur in the bottom 
	 area of the client window.</p></li>
</ol>
<h3>Exercises</h3>
<ul type="disc">
	<li><p>Add items to an existing subscription.</p></li>
	<li><p>Remove items from an existing subscription.<br />
	Tip: use the context-menu in the subscription area of the client window.</p></li>
	<li><p>Change the properties of items within a subscription to enable/disable 
	 per item etc.</p></li>
</ul>
<h1>Security</h1>
<p>To learn how to configure an application to trust or not-trust other 
 applications simply refer to the <a href="OverviewSecuringApplications.htm">Securing 
 Applications Tutorial</a>.</p>
<h1>Summary</h1>
<p>There are many, many other features of OPC that are not described here, 
 although some are mentioned throughout this help documentation. </p>
<p>For more information about OPC <?rh-udv_start name="TechnologyName" ?>Unified Architecture<?rh-udv_end ?> 
 features and capabilities see <a href="About_TechnologyName.htm">About 
 Unified Architecture</a>.</p>
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